The biggest irony of Albany’s push to delink student test scores from teacher evaluations — as a bill passed Thursday by the Senate Education Committee would do — isn’t that Gov. Andrew Cuomo now wants credit for the effort, after having championed the linkage for years. It’s that Cuomo’s war to make the scores count was lost long ago, so why bother to make it official?

From the start, the 2010 state law calling for test results to figure into teacher ratings was a sham. Cuomo himself later called it “unworkable by design.” Its real goal was to snag $700 million in federal “Race to the Top” money, and moving toward evaluations based on test scores was required for that.

Since then, the mandate has been delayed, revised, superseded and suspended so often it might as well never have existed. United Federation of Teachers boss Mike Mulgrew even admitted he deliberately “gummed up” talks with Team Bloomberg to stop it from taking effect in the city.

New York’s teachers unions were simply never going to allow their members to be graded in any serious, objective way, let alone fired on the basis of their performance. Indeed, to this day, poor student scores on state tests haven’t led to a single teacher being terminated under that 2010 law or any of its updates.

The latest “moratorium” isn’t even set to expire until next year. And if the test score-eval linkage were to take hold (no chance of that), the unions would still have another two years to delay it again, before any teacher could face consequences.

Meanwhile, in every year since 2012, unreformed evaluations have deemed no more than 1 percent of teachers to be “ineffective.” That’s not because 99 percent of teachers are stellar or kids are so high-performing: Last year, 60 percent of students flunked state exams.

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No, teachers are forever nothing but terrific, never mind that hundreds of thousands of kids flounder.

But the unions want to remove any possibility that scores may one day be used to purge bad apples — and lawmakers are eager to deliver. The Assembly has already passed the bill to delink test results from evaluations, and 55 of the 63 senators are co-sponsors.

As for the state’s most vocal advocate of the reform, Cuomo now practically claims the drive to repeal it was his idea: His staff has been “working with the Legislature and education community for months” on the issue, an aide said.

It comes down to this: Incompetent teachers in the regular public schools simply can’t be fired in New York. And any reform that materially threatens to change that will face the same overpowering opposition as the test-score law.

Cuomo’s cave-in, though, is particularly tragic, since he once posed as students’ last, best hope. He was determined, he said, to “break” the unions’ school “monopoly” and put students first.

In his very first year, he demanded new “measures and accountability” — “growth on test scores,” in particular — to judge teacher performance. “We’re going to persevere,” he vowed.

In 2012, Cuomo pushed through a law to fix the 2010 farce. It would be “a national model” for accountability, he vowed, setting “clear standards for measuring educators based on how our students are performing in the classroom.”

When that “fix” also failed, he demanded a still tougher law, asking: “How is the current teacher-evaluation system credible when only 1 percent of teachers are rated ineffective?”

The next year, despite fierce opposition, he pushed through an even more rigorous requirement: Test results would now count for fully 50 percent of a teacher’s rating, up from 20 percent.

Yet again, his foes won out: New Common Core standards had led to lower test scores, and the teachers unions got parents to “opt out” their kids from the testing. The Regents responded quickly — with Cuomo’s blessing — imposing yet a new delay in using the scores.

True, test results aren’t a perfect indicator of teacher performance. The idea was but a crude attempt to get around the political obstacles to identifying and firing weak teachers.

But the sad truth is that union power guarantees that no evaluation system will ever see more than a handful of the state’s teachers rated “ineffective.” Whatever the Legislature now offers will still leave rotten teachers in place — and kids cheated. Count on it.